Preparation of nu-cycloalkenyl carbamates



Patented Feb. 18, 1947 PREPARATION OF N-CYCLOKL'KENY L CARBAMATE'S em.E..Schw eit zer, Wihnington,;l1el.,;assignor to LE. .1. du Pont de.Nemours & C a m n ton, Del a corporation of Delaware No Drawing.Application May 27, 1944, Serial No. 537,742

(Cl. 260F468) 8 Claims.

invention relates to the preparation 01 .carbq yclic nitro encompunds..:andpa t cula ly to a novel method for preparin a ky -crclmallrenyl carbamates and related substances.

Heretofore ethyl N -cyclghgxenyl carbamate has been preparedby reactionbetween the diethyl ketal of cyclohexanone and ethyl carbamate in thepresence ,of an anilinehydrochloride catalyst .(Hoch, Compt. .Rend. 201,560-2 (1935) Pyrolysis of the resultant .alkyl vN-cyclohexenylcarba'mate gave cyclohexenyl isocyanate, hence by heating theprimaryreaction product under suitable conditionatthe unsaturatedisoqyanate could be obtamed. This method for the preparationoihalkylN-cycloalkenyl carbamates and cycloalkenyl isocyanafltes had thedisadvantage of requiring the intermediate preparation of cyc'loalkanoneke'tal, which was a relatively expensive and somewhat tedious operation;Because the alkyl-N-cycloalkenyl carbamates in the past were notreadily'available, they were of littl or no interest from a commercialstandpoint.

An object ofthis'invention is to overcome .the aforesaid disadvantages"of the above-described method for preparing jal N-. cyclohexenylcarbamates and 'cycloalkenyl 'isocyanates. Another object is toprovide'an economically feasible process for preparing these compounds. *Gthe'robpects of the invention will appear hereinafter.

The objects of the invention are accomplished by subjecting acarbocyclic ketone to reaction with an alkyl carbama'te, whereby analkyl -N- cycloalkenyl carbama-teis produced. It has'been discoveredthat inthe synthesis of alkyl N-cycloallgenyl carbamates it isunnecessary toemploy the cycloaliphatic ketal as a reactant hut-thatgood results may be obtained simply jby reacting the cycloaliphaticketone with alkyhcarbamate. The reaction is illustrated in the case ofcyclohexanoneby means of the following equation (R being an alkyl group).The alkvltvcloalkenyl.carbamatesithus ,produced may be isolated by. lowpressureldEtillationeof the reaction product. Disti lation of theproductat ordinary pressures results in the-formation 502i 5 .cv 1 a1 eny-.-1s0cvan.ate.-.wl 1 ma e mm as indicated ;inthe ;;following equation:

H 9% H 6 (i-N-C 00R H4) "(B-'N-CO rk o 1 .HSC OH Ron iC "LC :11, H:Alkyl N-cyclohexenyl tCyclohexenyl isocyanate carbamate l :In thesynthesis of alkyd .NaQYflcalkenylearbamates andicycloa'lkenyl,isocyanates in accord- ,ance with this invention thecycloaliphaticgketone and 'alkyl .carbamate are preferably heated ;:to,-gether in the presence :of an acid-reacting catalyst. In carrying out:this synthesis-it is gen;- erally desirable that the water produced byine reaction of the ketone and alkyl carbamate the withdrawn from themixture while the reaction is in progress. Atconvenient procedure-istoheat the reactants and the acidic catalyst in a :tillation vessel,whereby the water 'produced'by the .reaction can be :removed while thereaction is taking place. 7

The ketones which may be employediasreaotants in accordance with theinvention include cyclopentanone, cyclohexanone, methyleyclopentan-ones,l-imethylcyclohexanones, vcycloheptanone and the like. Thealkylcarbamate reactants'inelude :the lower alkyl carbamatessuch as nethylcarbamate, ethyl carbamate. isobutyl carbamate. :amyl carbamate and thelikens well-as the long chain alkyl carbamates,such as laurylcarbamate;Theacid-reacting catalysts include mineral. acids, such as hydrochloricacid, sulfuricacid, -phosphonic acid and organic acid-V-reactingsubstance such as toluene sulfonic acid, pyridine hydrochloride, ethylhydrogen sulfate. benzene 111 .fonic acid, aniline hydrochloride, and--the dike.

The reaction ;is generally conducted at .-a temperature withinthe-rangeof 7 5 to 20.0,-C.,preiaerably about .100" to C. The reaction-pressuremay be within the-range of about v12,0 ;m-il limeters to1800mi11imeters,absolute. --Preferably the pressure is lowered as the reaction proceeds,

so as to facilitate removal of water, and thereby drive the reactiontowards completion. Thus the pressure may be about-760 millimetersatithestfi it of the reaction,;and mayheprogressively. lowered .over aperiod of several hours until a final-pipes .sureof about .20millimeters is reached. .Inthis manner water removal -is accomplishedb,y tillation without texcessivewaporizationt and of the reactants. ifit is desired to separate 1. al-

'- 1 'Ihe, reaction between;

"the alkyl earbamate may beconducted either I claim: 7 I 1. In a processfor preparing alkyl carbocyclic nitrogen compounds, the steps whichcomprise subjecting a carbocyclic ketone of the class conproportions,but it is generally preferred to employ a slight excess of the alkylcarbamate reactant. Satisfactory results are obtained when;

the molal proportion of alkyl carbamate tocyclic ketone is initiallyabout 2 to 1. The amount of acid-reacting catalyst is rally" {abou't-1.0'to

5.0%, preferably about to "250%; of l't hetotal weight of the reactants.

The invention is further illustrated ,by means of the followingexamples, in which parts areby weight except as otherwise stated.

Example 1.A mixture containmg 49 teaser" cyclohexanone, 89 parts ofethyl carbamate and 2- parts 6f aniline hydrochlorideiwasheated in astill for 8 hours at a temperature of 115 C. V During this time thepressure was gradually reduced from atmospheric pressure to 50millimeters, and water was removed from thereaction mixture periodicallyby distillation. Finally, the pressure'reducedto 21 millimeters, and a,distillate containing eth'yl N-cyclohexenyl carbamate was collected ata'temperature of 1&5? C. (y'ield 46% based'uponcyclohexanone). 1;

Example 2.A mixture containing 49 parts of cyciohexarionatae parts ofethyl carbamate and 2 parts of anilin hydrochloride was heated in astill for-a-hours' at a temperature of 1 15 C. During this i time i thepressure was gradually reducedfromatmospheric pressure to 50 millirmeters and water-w'as removed from the-reactioni mixtu're periodicallyby distillation. 'The pressure was allowed toincrease to 400millifzi'lters'iand the temperature-of the reaction mixture was raisedto. 200 C.,-whereby a distillate containing cyclohexenyl l isocyanate"was produced; i Redis'tillation of thedistillate gave pure byclohexenylisocyanateiBg P.-= 61 at 17 millimeters) in 40% yield based onthecyclohexanone "liritially chargedfi 5 i i! L I above examples areintended to be illus- -on1y,"-ror it-is'evident that several differ- 'emodifications of the invention will occur to se skill'ed in the art.Thus,-- various methods in y e empicyearor:removing water 1mm: thereaction 'mixture'andthereby driving thereaction ltowards completion; Ifdesired, water -may be removed 'from the --reaction mixture by the use pof "materialswhich form relatively L low-boiling 'az'e'otropes withwater.

thel cycloalkanone and -batchwise or continuously. v Any suitableapparams may be employed, such as a-vacuum still in batchwiseoper'ation,or'a-fallingfilm type conve'rt'er in the continuous process 1 I J 1i'I-he alkyl N -cy'cloalkenyl carbama'tes and the cycloalkenyli'socyanates which 'are prepared iii a'ccordancewith this invention maybeused .forfvarious" purposes; "such as reagents: for :theimprovement-of textiles, resin intermediates, oxid'ati'on inhibitors'for lubricating oils,- and re- --'agents for introducing ethyleniclinkages into resins containing-hydroxyl groups. 5 3 I lt will beunderstood-that many diiferent embodiments of this invention may be madewithout departing from the spirit and scope thereof and m the followinglaimsk t-hat we do not limit ourselves except'fa s set forth i mixturewhile the reaction is in progress whereby an alkylN-cycloalkenylcarbamate is formed.

'j 21. 1?! 'aprocess for preparing alkyl carbocyclic nitrogen,compounds, the steps which comprise subjecting a carbocyclic ketone ofthe class consisting oflcyclopentanone, cyclohexanone, methylcyclopentanones, methylcyclohexanones and cycloheptanone to reaction withan alkyl carbalmateiin the presence of an acid-reacting catalyst andwithdrawing water from the reaction mixture while the reaction is inprogress whereby an alkyl N-cycloalkenyl carbarnate is formed. M

i 3. g In a process for preparing alkyl 'c'arbocycllc nitrogen"icompoundsfthe steps which I comprise subjeoting'a carbocyclic'kto'neb*tn elf sisting of cycldpentanone, cycloliexanone,-'nit h ymy m manenes;ma 'ylc crenexaabiies i a cir lene e gi a n wi h wasta e ma i he-Pence9fai a k wt e cata y t t a at re it n t ien wfi? o: 0;." nd wi hrawingi ate :i n thei'r acti; m xture w i h ea t on i 'li q' r e h by al l N-ev l k n lnar.amate 5 i p e s. re ring. al y Nrlc cloai se ylcarbamates which comprises subjecting a, car; q l c c ne 9f..theic1 's cnsisti g of icyc i Pen anon'e, ...cyc o a one. methylcyclopentag nones,methylcyclohexanone'siand;cyclohepta Pres nc 9 ahns ewre withmiil erange. .ii li zw terfirem,them s. gressively diminishing the pres re. asthe -re tion proceeds and distilling amym eyuoalgjiyi gra mes h iresultai tl i q fii i Mea ur e QWa O E se d lifiis l i lowOQmillimeters.-- V fi-A; essfq p eparin -a ylyizyci e xir t mina es wh h:c mp s s.-subi fi n e iqlq hexanone' t reaction hemalk l rwba nete inthe presence'of an acid reacting catalyst at a temperature within therange of 75 to 209 C., distilling water from the reaction mixturebyprogressively diminishing-the pressure as=the read-.-

' tion proceeds, and distilling alkyl N-cycloalkenyl carbaniate from"the resultant reaction xture at a temperature below 200 C. and apressure below 400 millimeters. j 7. A process for preparing alkylcyclohexenyl carbamates which comprises subjecting cyclohexan'one to:reactionwithianilalkylcarbamate in the; presence of an acidlrgactingcatalyst eta temperature Within the; range Of-' aHOfit IOO -ti) 1-2520.; and at a progressively diminisneepfes sure within the range from thereaction mixture at a temperature below 200 C. and a pressure below 400millimeters. 1

8. A process for preparing ethyl N-cyclohexenyl carbamate whichcomprises subjecting cyclohexanone to reaction with ethyl carbamate inthe presence of an acid reacting catalyst at a temperature within therange of about 100 to" 125 C., at a progressively diminished pressurewithin the range of 50 millimeters to atmospheric pressure, removingwater from the reaction mixturebydistillation, and distilling ethylN-cyclohexenyl carbamate from the resultant mixture of 20 millimeters to800 millimeters, removing water from the reactin mixture by distillationandthereafter distilling, the resultant alkyl N-cyclohexenyl carbamate'V The following referencesare of record in the .at a temperaturebelow'200" C. and below 400 millimeters.

CARL E. scHwE'rrzE 1 REFERENCES crrnn file of this patent:

1 Number Strain J our. of the American Chemical Soci- FOREIGN PATENTSCountry Date British May 24, 1938 OTHER REFERENCES ety, vol. 52, p. 820to 823 (1930).

Bischoff, 634.

Berichte, volume '7 (1874); page a pressure

